Stardate 52645.7: With Odo knocking at passing's door, scant time remains to find a cure. In an effort to lure Section 31 out of hiding to obtain the vaccine, Doctor Bashir and Chief O'Brien have gone behind Captain Sisko's back. Now, telling him about their plan, Doctor Bashir informs Sisko that Section 31 is the only hope that Odo has left.
When the Cardassian occupation of Bajor ended in 2369, the mining space station Terok Nor was left abandoned, its systems ripped out. By invitation of the Bajoran provisional government, Starfleet stepped in to oversee the rebuilding and day-to-day operations of the newly christened Deep Space Nine.
The years of Starfleet's nonintervention into Cardassian matters, however, had taken its toll on relations with the Bajorans. Consequently, Starfleet's position was a tenuous one; many Bajorans, suspicious and hostile as a result of decades of Cardassian oppression and brutality, did not greet the Federation's presence with open arms. The Federation's assistance is put to the test as DS9 becomes a center of travel and commerce that stretches into the Gamma Quadrant.